The invention relates to methods and compositions for repairing bituminous wearing courses, such as asphalt or tarmacadam roads and carparks.
Bituminous wearing courses such as asphalt are generally composed of about 94% aggregate (gravel or sand) and about 6% bitumen binder. The bitumen binder is composed of hydrocarbons and has ionic properties, which serve to bind the sand and gravel particles together.
Wearing courses deteriorate through oxidation of the bituminous binder. The oxidation process reduces the ionic properties of the bitumen, which in turn leads to release of the aggregate. The oxidised binder loses its flexibility and the surface shrinks and cracks. The effects of traffic and weather (temperature changes and moisture) speed up this process. After general release of material larger flaws appear which eventually turn into potholes.
The oxidisation process accelerates other damage to the wearing course and failure of joints especially from conventional reinstatements, around ironwork and on trenchwork.
The conventional method for repair to damaged or aged asphalt and tarmacadam wearing courses comprises digging out of the asphalt by planing, saw cutting or with a jackhammer (pneumatic drill). The removed asphalt is disposed of and the area is made good with new material which then needs to be compacted and sealed with overbanding or jointing sealant. This conventional method is not ideal in respect of cost, safety, environment, sustainability and durability.
The invention provides an improved method for repairing a damaged area of a bituminous wearing course. The method comprises
(i) heating the damaged area;
(ii) applying a liquid to the damaged area that rejuvenates damaged bitumen;
(iii) adding new material to the damaged area; and
(iv) compacting the new material.
The method preferably also comprises:
(v) applying a topcoating liquid to the repaired area which seals and binds the repair; and/or
(vi) applying a fine aggregate to provide skid resistance.
The invention may be applied to any bituminous wearing course. The wearing course may be asphalt or tarmacadam, for example on the surface of a road, carpark, pavement, airfield, railway station platform or driveway. The method of the invention is particularly suited to repairing potholes but it may, for example, equally be used to repair a trench, failed joint or failed seam.
The invention also provides a composition which can serve as the rejuvenating liquid for use in the method. The composition may comprise an emulsifier, a heavy paraffinic distillate solvent extract, a heavy naphthenic distillate solvent extract, a naturally occuring mineral asphalt and water.